Double-blind RCTs showed significant improvement vs placebo in erectile function and successful intercourse attempts with on-demand sildenafil (25–100 mg).
View RCT (NEJM)

Randomized trials show tadalafil improves erections and maintains responsiveness up to ~36 hours post-dose—useful for flexible timing (“weekend” window).
View RCT (Urology)

A meta-analysis of direct comparisons found similar efficacy and adverse-event rates. Some studies favored tadalafil on psychological outcomes and partner satisfaction.
View Meta-analysis (Int J Clin Pract)

A large network meta-analysis of 179 RCTs found all PDE5 inhibitors outperform placebo. Dose-response patterns varied; both tadalafil and sildenafil had strong benefit profiles across common doses.
View Network Meta-analysis (2021)

Systematic reviews also support efficacy in certain groups (e.g., spinal cord injury–related ED), though study quality varies. Care is individualized.
View Systematic Review (Spinal Cord)

At high altitude, sildenafil can reduce hypoxic pulmonary hypertension and improve exercise capacity in some settings/subjects.
View RCT (Ann Intern Med, 2004)
View RCT (Am J Respir Crit Care Med, 2005)

In trained cyclists, sildenafil did not improve a 16.1 km time-trial at sea level or moderate simulated altitude; benefits seem context-specific and not reliable for normal gym performance.
View RCT (2019)

• Efficacy: Both tadalafil and sildenafil are well-supported by RCTs for ED.
• Choice: Similar efficacy; tadalafil offers a longer window. Your provider will tailor dose/timing and review interactions (e.g., no nitrates).
• Performance: Not a gym enhancer at sea level; some altitude-specific data exist but don’t translate to everyday training.